1. Field of the Invention
This invention relates to the field of robotics. There are many types of robots. Some remote control or autonomous boats, submarines, vehicles, aircraft, or missiles are considered robots. Some computer numerically controlled automated mills, lathes, or other machinery are considered robots. And sometimes a simple non-moving electronic device, modem, computer, or data server is called a robot. This invention is specifically about robots, either whole or part of a whole, that have at least one articulated joint, including, but not limited to, SCARA robots, Stewart platforms, pick-and-place robots, animatronic robots, legged robots, armed robots, anthropomorphic robots, animal robots, fish robots, insect robots, motion controlled camera jibs and cranes, space exploration robots, firefighting robots, toy robots, military robots, industrial robots, welding robots, painting robots, prosthetics, exoskeleton robots, crash dummies, medical robots, anatomical models, stunt doubles, and ballistics targets.
2. Description of the Prior Art
The majority of articulated motion in robots is designed with revolute joints. A revolute joint has a single axis. The moving structures in a robot with revolute joints are held together with an axle or a pin in such a way as to allow for one part to move relative to another part about a single axis. The engineering of such revolute joints can be highly precise, low friction, easily measured with sensors, well understood, and easy to model computationally. Joints with bearings, when affordable, help reduce friction, but the resulting motion, about a single axis, is essentially the same, and are also revolute joints.
Many complex motions done by a human body, such as the motions of the shoulder, are typically deconstructed into an arrangement of three or more revolute joints with orthogonal axes, such as the shoulder in U.S. Pat. No. 8,322,250 (Kim).
Although revolute joints prevail, there are a few alternatives. U.S. Pat. No. 4,815,911 (Bengtsson) describes a robotic arm comprising pinless joints having contact surfaces held together by spring-like harnesses. The surfaces are frictionally engaged and roll upon one another without slippage.
In U.S. Pat. No. 2,500,614 (Lohmann) an artificial hand is described that uses spherical shapes rather than an axle or pin as part of the articulating fingers.
Compliancy in the motion of a robot is important. U.S. Pat. No. 8,606,398 (Eakins), for example, introduces compliancy into a robotic manipulator by adjusting the pressure of a balloon that couples the arm to the gripper.
Most robots designed to mimic the appearance and or motion of a human are inspired by an elementary external survey of human body parts. Thumb, fingers, palm, wrist, forearm, elbow, upper arm, shoulder, torso, legs, feet are the typical elements of these inventions. U.S. Pat. No. 8,511,964 (Linn) outlines these body parts in the claims, with an additional shrug element.